95 LT1 issues

[mistafosta]

Working on a 95 LT1 and having a hell of a time with this idle problem.

Car runs great under partial throttle and full throttle, but at idle it gets a intermittent dead hole (You can listen to it run then miss, then run fine again)

History of the car is that it has a new opti/opti harness/wires/plugs/fuel filter, recently replaced headgaskets and a temp sensor (That caused the original headgasket failure) The car had a full dead miss when it came it (Caused by the headgasket failure i believe) I tested out other injectors but had the same result.

Any ideas? This car needs to leave and this is all I have left to do so I can smog it. Also the car was sitting for a long time, but I swapped out the gas for new stuff so old gas shouldnt be the issue.

I checked vacuum lines and for any plug arcing also. Maybe its a PCM or ICM issue?

[c4c5specialist]

Hi there,

Did you check the engine data???

Crankshaft position sensor might be an issue. The optispark, was it a GM unit ?

I would check the compression of all cylinders since a slight leak would present it as a miss only at idle.

Allthebest, c4c5

[mistafosta]

Originally Posted by c4c5specialist

Hi there,

Did you check the engine data???

Crankshaft position sensor might be an issue. The optispark, was it a GM unit ?

I would check the compression of all cylinders since a slight leak would present it as a miss only at idle.

Allthebest, c4c5

The optispark is a summit brand opti, but I swapped it twice with zero result change so Im really leaning away from that being the cause.

I don't have a scanner, so I haven't been able to check out the data. I'm gonna try to swing it by my friends shop tomorrow.

Would the CPS show any other issues? Isn't that based off the optispark readings?

Ill try to get compressing readings tomorrow also if I get a chance

[mistafosta]

ok, checked compression, they are within 10% the lowest being 180, highest being 190. I also swapped in a known good ICM, PCM, and MAF with no change in the issue. Could it possibly be a defective plug or wire?

Plugs looked very clean as well, none look like they have a missfire going on. (At least not from no spark)

[lovehatec4]

Originally Posted by mistafosta

ok, checked compression, they are within 10% the lowest being 180, highest being 190. I also swapped in a known good ICM, PCM, and MAF with no change in the issue. Could it possibly be a defective plug or wire?

Plugs looked very clean as well, none look like they have a missfire going on. (At least not from no spark)

Use an ohmeter to check your plug wires. The longer the wire the more ohms. Also check that crank sensor. They sometimes get crud on the magnet causing failure or weak signal. Also, check your base timing and idle air controller. And if its got those high dollar aftermarket sparkplugs, replace them for stock ac plugs. These cars need the oe type to run correct (if stock).
Let us know..

[lt14life]

Originally Posted by lovehatec4

Use an ohmeter to check your plug wires. The longer the wire the more ohms. Also check that crank sensor. They sometimes get crud on the magnet causing failure or weak signal. Also, check your base timing and idle air controller. And if its got those high dollar aftermarket sparkplugs, replace them for stock ac plugs. These cars need the oe type to run correct (if stock).
Let us know..

You made a good point about the Plugs, I installed the E3 plugs and it ran great , now I have a rough idle issue going on with my 94 but when it warms up it runs perfect , I have replaced the Opti, ICM which tested bad, IAC Valve, Coil. And all pigtail connecters, & Spark Plug Wires, All the wiring & Connections look good.